1. Field of the Invention
The present invention relates to a locking mechanism for electrical connectors, more especially to a locking mechanism for electrical connectors having a conductive connector case.
2. Description of the Prior Art
Most of the latest electronic systems having a computer precision electronic circuit require some protection against electrostatic damage. Especially, precision electronic circuits having an IC or LSI are prone to electrostatic damage, causing a malfunction or breakdown.
FIG. 12 shows one of the conventional electrical connectors having a mechanism for protecting electronic circuits from electrostatic damage. A plug connector 15 is secured to a cable 30 having a shield wire 31 and lead wires 32. This plug connector has at the front end a plug unit 16 having contacts therein and a plug case 17 made of metal and attached to the back of plug unit 16. A receptacle connector 20 is secured to the housing of an electronic system 40. It has at its front end a receptacle unit 21 having contacts therein and a receptacle case 22 made of metal and attached to the back of plug unit 21.
As a protective means against electrostatic damge, a lead wire 33, which has been connected to the shield wire 31, is connected to the housing of electronic system 40 with a screw 45 or the like, while the shield wire 31 is secured to the plug case 17. A lead wire 42 connects the receptacle case 22 of receptacle connector 20 to the housing of electronic system 40. Reference numeral 41 denotes an electronic circuit connected to the contacts of receptacle connector 20.
With such a structure, even if a person having static electricity holds the plug connector 15 and inserts it into the receptacle connector 20, the static electricity is grounded through the shield wire 31, lead wire 33, and the housing of electronic system 40 so that it has no adverse effects on the electronic circuit 41.
There are many mechanisms for locking the connection of these connectors. For example, Japanese U.M. Patent Publication No. 53-47580 discloses a mechanism having a locking member fitted into the connector case for easy attachment and detachment without using a bolt. This mechanism will be described in connection with the accompanying drawing, wherein FIG. 13 is a perspective view of the locking member; FIG. 14 is an elevational section showing the locking member installed in a connector housing in which the locking members are fitted, and FIG. 15 is a sectional view taken along the line 15--15 of FIG. 14.
As FIGS. 14 and 15 shows, this conventional boltless connector locking mechanism has a pair of locking members 1. This locking member has at one end a hook-like engaging portion 2 and at the other end a pushing portion 3. It is provided at opposite sides with a pair of resilient strips 4 and 4' made of a flexible material. As shown, these resilient strips are made integral with but narrower than the locking member 1 so that they may be more flexible than the locking member. A reinforcing rib 5 is provided in the locking member 1 so that the locking member may be more rigid than the resilient strips. The case is made up of two case halves 6 and 6', each having a pair of pockets 7 and 7' into which the front ends of resilient strips 4 and 4' are fitted.
When each locking member 1 is installed in the case by inserting the resilient strips 4 and 4' into the pockets 7 and 7', the hook portion 2 engages a lockpiece 8 (8') while the pushing portion 3 is exposed through a window 9. In FIG. 13, when the pushing portions 3 are pinched inward into the window 9, the resilient strips 4 and 4', the front ends of which have been fitted into the pockets 7 and 7', are bent between the fitted portions and joints 10 and 10' so that the hook portions 2 move outward and disengages from the lock pieces 8 and 8', thus releasing the connector lock.
However, such conventional electrical connectors have the following problems: In FIG. 12, the plug connector 15 is secured mechanically as well as electrically to the electronic system 40 through the lead wire 33 so that its handling has been very inconvenient. Especially, when the plug connector 15 is to be connected to another receptacle connector, the screw 45 must be loosened to remove the lead wire 33, and then the plug connector is connected to another receptacle by screwing the lead wire 33 to the other system. In addition, when the plug connector 15 is disconnected from the receptacle connector 20 when they are not used, the lead wire 33 bears the combined weights of plug connector 15 and cable 30 and can be broken by accident.
In FIGS. 13 and 14, the hook-like end 2 of locking member 1, which is installed in the vicinity of the opening of the case 6 and 6' and free to move inward within the case in FIG. 14, can be bent toward inward by an external force applied upon connection. If the hook portion 2 is engaged with or disengaged from the locking piece 8 or 8' by an undue force, it can be deformed. Such bending or deformation will result in a defective connection between plug and receptacle connectors.